通过EnumWindows枚举顶层窗口，并显示窗口信息

The EnumWindows function enumerates all top-level windows on the screen by passing the handle to each window, in turn, to an application-defined callback function. EnumWindows continues until the last top-level window is enumerated or the callback function returns FALSE.
这是MSDN上关于EnumWindows函数的解释，意思是枚举所有处于顶层的窗口，但是什么是顶层窗口我并不是十分了解，因为从程序运行的结果我看不出所谓顶层窗口有什么共性，需要再研究研究，程序代码如下：

#include <windows.h>
char om[262144];
BOOL CALLBACK EnumWindowProc(HWND hWnd,LPARAM lParam);
BOOL CALLBACK EnumChildWindowProc(HWND hWnd,LPARAM lParam);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
    HWND nphWnd=::FindWindow("notepad",NULL);
    if(nphWnd)
    {
        ::EnumWindows(EnumWindowProc,0);//枚举窗口
        ::EnumChildWindows(nphWnd,EnumChildWindowProc,0);
    }
    return 0;
}
BOOL CALLBACK EnumWindowProc(HWND hWnd,LPARAM lParam)//枚举窗口的回调函数
{
    char temp1[256];
    char WinClassName[256];
    ::GetClassName(hWnd,WinClassName,255);//获得类名
    DWORD pID=0;
    ::GetWindowThreadProcessId(hWnd,(LPDWORD)&pID);//获得进程ID
    ::GetWindowText(hWnd,temp1,255);//获得窗口标题
    ::wsprintf(om,"%s%s%s%s%s%s%d",om,"\r\nclassname: ",WinClassName,",wintext: ",temp1,",ID:",pID);
    return true;
}
BOOL CALLBACK EnumChildWindowProc(HWND hWnd,LPARAM lParam)
{
    char temp1[256];
    if(hWnd)
    {
        ::GetClassName(hWnd,temp1,255);
        if(!::strcmp(temp1,"Edit"))
        {
            ::SendMessage(hWnd,WM_SETTEXT,0,(LPARAM)om);
            return 0;
        }
    }
    return true;
}